The present invention relates to a guiding device for a printing sleeve or cylinder, particularly for flexographic printing as well as the sleeves or cylinders provided with this device.
In the case of sleeves for example, it is known that they have considerable advantages from a point of view of weight, when they are made of a composite material, but there remains a problem, of attaching printing plates to the peripheral surface of the sleeve.
Thus, the surface of the sleeves is precision ground to give it a suitable finished condition and above all such that the development, connected to the precision of the diameter, corresponds nicely to the desired development. However, it is necessary to avoid any false round which could militate against the precision of contact of the printing plate on the transfer roller or with the surface to be printed.
It is also known that printing plates must be perfectly positioned. These printing plates are thinner and thinner for evident reasons of material cost but also to improve the quality of the screen.
Because of this, as the quality increases and the length of delays in emplacing the sleeves are reduced, it is increasingly necessary to provide suitable means for holding the printing plate on the sleeve.
In a known manner, the printing plate is connected to the sleeve with double-faced adhesive. Reference marks are integrated in the printing plate at the time of manufacture, which reference marks are to be brought into coincidence with those on the sleeve.
After gluing the printing plate on the sleeve, it is necessary to cut the double-faced adhesive which protrudes, by cutting it off as evenly as possible. Most of the time, this cutting off is carried out manually by the operator, with the aid of a cutting blade, which has the immediate consequence of leading to score lines on the external coating of the sleeve.
When the wear is sufficiently great, it is generally necessary to send the sleeve to the factory to redo it, which, in addition to being a loss of time and a loss of use of the set of sleeves, is needlessly expensive.
Moreover, it is easy to see that the cutting-off is relatively delicate because any slip of the blade can lead to damage to the printing plate.
The present invention overcomes these drawbacks by means of an integrated guiding device for mounting printing plates and for cutting. The device is very practical for the user, and permits adjustments and cuts both along generatrices and along circumferences The device is of a cost altogether compatible with the price of the supports, sleeves or cylinders, whose amortization is almost immediate. The device is neutral relative to the mechanical resistance of the sleeve with the cylinder, and is also self-compensating as to balancing and is applicable to all products free from surface fibers.
To this end, according to the invention, there is disclosed an integrated guiding device for the emplacement and cutting, with the aid of a cutting tool, of a printing plate on a printing sleeve or cylinder, particularly for flexography. The sleeve or cylinder has an external coating adapted to be deeply machined. The guiding device has at least one longitudinal guide, along a generatrix, and/or a peripheral guide, about a circumference, provided within a matrix of very hard material. The matrix is held within the thickness of the external coating.
According to a preferred embodiment, the matrix of very hard material is disposed in a throat machined in the thickness of the external coating.
More particularly, the throat comprises immobilization means in the thickness of the coating, for example a dovetail profile.
The guide has a cross-section adapted to the profile of that of the cutting tool.
According to another characteristic, the matrix is made of a polymeric material loaded with particles of metal and/or ceramic.
The invention also relates to the sleeve or cylinder provided with this device.